1. Field of the Invention
The present invention relates generally to reflective surfaces, and more particularly but not exclusively to reflective surfaces employed in light modulators.
2. Description of the Background Art
Light modulators fabricated using micro electromechanical system (MEMS) technology, in general, are well known. Examples of such light modulators include the Grating Light Valve™ (GLV™) light modulator available from Silicon Light Machines, Inc., and the digital micro-mirror device available from Texas Instruments, Inc. GLV™ light modulators employ a plurality of ribbons to reflect or diffract incident light. Devices that are of the same type as GLV™ light modulators are hereinafter referred to as “ribbon light modulators”. Ribbon light modulators are described in the following disclosures, which are incorporated herein by reference in their entirety: U.S. Pat. No. 5,311,360 to Bloom et al.; U.S. Pat. No. 5,841,579 to Bloom et al.; and U.S. Pat. No. 5,661,592 to Bornstein et al. Ribbon light modulators and micro-mirrors can be employed in various applications including optical networks, manufacturing, data storage, video, and printing. As can be appreciated, it is advantageous to optimize a light modulator for a specific application.
Ribbon light modulators have been employed in printing applications. In one printing application, a laser beam is bounced off a reflective surface of a ribbon light modulator and onto a plate. The laser beam has a wavelength ranging from 800 nm to 830 nm, and a power density of about 2 kW/cm2, which, when focused, is sufficient to expose the plate. The ribbon light modulator is actuated to modulate the laser beam and form a pattern on the plate. The plate is inked and rolled onto paper to transfer the pattern thereon. The Xcalibur 45™ platesetter from the Agfa Corporation employs such a ribbon light modulator. In the just-mentioned printing application, the ribbon light modulator has a reflective surface of aluminum alloy consisting 99.5% aluminum and 0.5% Copper (Al—Cu(0.5%)). The copper in the aluminum alloy is believed to minimize aluminum diffusion, thereby making the ribbon light modulator less susceptible to damage caused by large thermal gradients. The use of a ribbon light modulator in a printing application is also disclosed in U.S. Pat. No. 6,229,650.